An organic electroluminescent device (OLED) has the advantages of simple structure, high yield, low cost, and active light emission, etc., thus becomes a hot topic in the field of flat panel display in recent years.
In an OLED preparation and optimization procedure, the choice of a luminescent material is essential; the property is one of the important factors determining the device performance. Currently, a condensed-cyclic compound is a classic fluorescent material, and also is one of the earliest luminescent materials found in an OLED device with an electroluminescent property and the most widely used.
The present inventors have found that in long-term studies, most of the condensed-cyclic compounds in the dissolved state have a strong fluorescence, while in aggregate state or solid state it has Aggregation-Caused Quenching (ACQ) phenomenon due to the non-radiative relaxation of the excited state of the aggregates. Also, in most industrial processes, ACQ effect is inevitable when a fluorescent material need to be prepared into aggregated, solid state, or thin film. Thus the application of such materials is greatly limited.